The traditional means for transporting freight such as coal or the like across the continental U.S. has been the railway car. The standard railway car for transporting coal includes a car body having two end walls and two side walls, a standard truck positioned at each end of the car body and coupling means for interconnecting the individual cars of a train. The centers of the trucks of coal cars are usually spaced 45 feet apart. The overall car body normally has a length of 50 to 55 feet. Center sills extend longitudinally along the underside of the car body between bolsters supported by the standard trucks. Center sills of this type are disclosed in U.S. Nos. 3,040,679, 3,102,497, 3,538,857, and 4,003,319.
Center sills of the type disclosed in the above patents are rigidly mounted to the railway car. These center sills cannot flex or bend to compensate for curves. Trains using rigid center sills must employ standard truck bolsters and couplings to enable the train to maneuver through curves. The standard couplings and bolsters form a considerable portion of the overall weight of the railway car. Prior to this invention it has not been known to use a flexible center sill for maneuvering curves.
Industry standards have imposed on railway companies maximum weight limits that may be distributed over a set of axles. The weight limit varies according to the specific class or size of the axles. The weight limit includes the weight of the railway car and the weight of the lading allocated to the set of axles. An inherent disadvantage in the use of conventional railway cars is that a significant portion of the weight limit must be allocated for the weight of the railway car. Consequently, the amount of freight which can be hauled is significantly reduced resulting in higher operating costs and diminished profits.